The present invention relates to a color image processor for inputting data about a halftone image of plural colors and performing rasterization.
Generally, colors are represented on colored materials by halftone processing using dithering. Where dithering is employed, binarization is performed by hardware and so the adopted method is to lay periodic rectangular dithered patterns over the whole image. Adoption of this method permits high-speed processing with a small amount of hardware. Accordingly, a full-color image is once rasterized into a memory buffer. After completion of the rasterization, binarization is performed again for the rectangular rasterized region.
With the prior art technique, however, if one attempts to perform a rasterization operation at the stage of two-valued rasterization without impairing the color hues, and if the method consists of two operations (i.e., one operation consists of completing multi-valued rasterization into a buffer memory; another operation is to then perform a binarization operation) is adopted, then two rasterization operations are required. This creates the problem that the processing time is long.
Where one attempts to perform a rasterization operation without impairing the color hues at the stage of two-valued rasterization processing, if binarization is performed after completion of multi-valued rasterization into a buffer memory, it is necessary to load data about the multi-valued image into the memory. Therefore, a large capacity of memory area is necessary for the buffer memory.
It is an object of the present invention to provide an image processor for realizing high-speed rasterization while maintaining the quality of the output image.
A color image processor in accordance with the present invention comprises an input circuit for receiving a Raster command involving Raster Operation codes and data about an image of multiple gray levels of plural colors, an UCR/BG circuit having UCR/BG functions of decomposing the data about the image of multiple gray levels of plural colors according to individual color materials of plural colors using the Raster Operation codes, rasterizing the decomposed data into a buffer memory, and generating black, and a binarization circuit having functions of binarizing raster data about each gray level and converting the raster data into data images each having one gray level.
Where the above-described Raster Operation codes are other than Raster Operation codes including a base image, the raster output function, the UCR/BG functions, and the binarization function described above are simultaneously performed.
Where an output image to be derived is a two-valued rectangular image, the UCR/BG circuit performs UCR processing on the raster data produced by the input circuit, as well as black generation. The raster data converted and undergone the black generation and the UCR processing are binarized by the binarization circuit and rasterized into the buffer memory.
If the output image to be obtained is a two-valued image and a Raster command involving ROP codes not having a base image as operation elements is received, and if the rasterized image is a rectangular image, then the raster output function, the UCR/BG functions, and the binarization function are not performed separately. Rather, they are performed simultaneously. If ROP codes including a base image are entered, raster data is created. Also, UCR/BG conversion is performed. Then, a binarization process is directly carried out. Data about a two-valued image is rasterized into the buffer memory.
In the present invention, if a Raster command which involves Raster Operation (ROP) codes not having a base image as operation elements is received, pixels are created. Then, UCR/BG conversion is performed, followed by dithering. Binarization is then effected. These steps are carried out in one operation.